In many less developed countries and in rural areas of many more developed countries, drinking water contamination is a serious problem leading to life threatening diseases. The resulting health problems are directly traceable to fecal contamination of the drinking water. Fecal contamination propagates waterborne diseases such as diarrhea, hepatitis and cholera, among others. This contributes to an infant mortality rate that exceeds by as much as ten times the rate in more developed countries. Fecal contamination of drinking water supply can result from multiple sources, such as animal excrement in rivers or, during dry seasons, in dry river beds located near drinking wells. The fecal contamination is then transferred to drinking wells from natural flow paths or from runoff during rainy seasons. Other transmission pathways include latrines situated near wells and non-hygienic drinking water containers within common areas where cups dipped into an open water container transfer bacteria from hands to the communal water supply.
Ultraviolet (UV) radiation sources have been found effective to sterilize water because of the wavelength of light emitted, typically centered around 254 nm, which is referred to as ultraviolet light or ultraviolet radiation. UV light represents a section of the overall electromagnetic spectrum of light, extending from the blue end of the visible at about 400 nm to a region of about 100 nm.
Prior point-of-use water sterilization devices typically are complex and costly, as well as not being suited for use in rural areas where simplicity, durability, and ease of operation are essential for sustained use. Some devices have employed heating systems to boil water, but are bulky and energy intensive. Other devices have more frequently employed the use of ultraviolet light to sterilize water. These include those shown and described in U.S. Pat. Nos. 7,030,391; 7,002,161; 7,002,140; 6,953,523; 6,193,894; 5,441,179 and 4,762,613 where some type of UV radiation is directed onto a supply of water, either by directing the water past the source of UV radiation or directing the UV radiation periodically at the water supply in a fixed chamber. The containers typically are expensive or the UV emitting radiation sources, such as elongated lamps, are encased in costly protective sheaths to prevent fouling from waterborne minerals or inactivated biological contaminants that can result from the photochemical reaction of the exposure of the UV radiation on the water. Alternatively the water sterilization devices will require costly wiper devices to clean the UV radiation source or periodic disassembly and delicate maintenance to maintain effectiveness. Emission or leaching of volatile organics from plastic wiper devices upon exposure to UV radiation is another disadvantage of prior art devices, such as the wiper device described in U.S. Pat. No. 4,002,918. Heat build-up in prior art devices has also been a problem that can affect performance. Accordingly, there is a need for a simple, low cost, reliable water purification device that may be employed in less developed nations and rural areas which requires minimal maintenance and is effective to supply a reliable source of purified drinking water.
These problems are solved in the design of the present invention which employs a low cost, simple and reliable design to purify water for drinking using UV radiation.